1. Field of the Invention
The present invention relates generally to the fields of virology, immunology and diagnostics. More particularly, it concerns antibodies directed to and antigens derived from flavivirus envelope protein domain III in compositions and methods for detection of various members of the genus flavivirus. 
2. Description of Related Art
West Nile virus (WN) is a member of the Japanese encephalitis (JE) serocomplex of the genus Flavivirus (Family Flaviviridae). This virus was first isolated from a febrile woman in the West Nile province of Uganda in 1937, and now has an almost worldwide distribution including parts of Africa, Asia, Europe and, most recently, North America. Kunjin virus, now re-classified as a subtype of West Nile virus, is found in Australasia.
Since 1999, the United States has experienced annual epidemics of WN disease in humans and animals over an expanding geographical range. WN virus has been isolated in 44 states, and more than 4,100 cases of human disease resulting in 284 deaths had been reported during 2002 (MMWR, 2002a). Several of these cases are suspected to have originated from virus transmitted during blood transfusion and/or organ transplantation (MMWR, 2002b). Outbreaks of WN disease with neurological manifestations have also been reported in Eastern Europe, North Africa and Israel since the mid-1990s (reviewed by Murgue et al., 2002).
Other members of the JE serocomplex include JE virus, found throughout Asia, St. Louis encephalitis (SLE) virus, found in the Americas, and Murray Valley encephalitis (MVE) virus, found in Australia and New Guinea. These viruses are antigenically similar to WN virus, and their co-circulation in several regions of the world has complicated the specific diagnosis of infections by these viruses in humans and other hosts (Fonseca et al., 1991; Martin et al., 2002). Current protocols for the serological diagnosis of WN virus infection in the United States rely primarily on preliminary screening for WN virus-reactive IgM/IgG antibody by capture ELISA and confirmation by plaque reduction neutralization test (PRNT) (CDC, 2001), a process which results in considerable delays in the reliable reporting of accurate case numbers, and requires the confirmatory testing to be performed in specialized laboratories.
Current diagnostic assays utilize either ELISA or dipstick formats for identification of flavivirus infection (PanBio, Integrated Diagnostics (Dobler et al., 1996, Niedrig et al., 2001, Yoshii et al., 2003)). A number of assays are available for the detection of dengue virus infection. These assays utilize antigen capture and antibody-based ELISAs and dipsticks for detection of virus specific IgG or IgM. Diagnosis of TBE infection depends on IgG-based ELISA assays that are available in Europe (Dobler et al., 1996, Niedrig et al., 2001, Yoshii et al., 2003). However, these tests have limitations with both sensitivity and cross-reactivity with other flaviviruses (Niedrig et al., 2001).
The recent utilization of subviral particles (SVP) in an ELISA-based diagnostic test for tick borne encephalitis TBE infection shows promise (Yoshii et al., 2003). Since this assay uses intact viral M and E proteins it is likely that the pitfalls that affect the use of complete viral antigen (e.g., cross-reactivity) may impede the employment of this assay in diagnostic settings.
The use of RT-PCR is also a potential method for diagnosis of flavivirus infection. However, RT-PCR assays have the significant limitation of requiring advanced techniques, equipment and reagents that require a cold-chain for stability. In addition, RT-PCR detects the presence of virus in patient serum, a condition that is not usually met when patients came to a hospital as the virus is frequently cleared from the bloodstream by the onset of symptoms. Clearly, there is a need to improve the current reagents used for diagnosis of West Nile and TBE virus infections.